1. Field of the Invention
This invention lies in the field of cutter apparatus for sheet materials, such as plaster board, and the like.
2. Prior Art
Cutting machines which employ a pair of cooperating opposed rotary disc knives adapted to form coinciding grooves on opposite sides of a sheet have been disclosed heretofore. For example, Preston U.S. Pat. No 898,259 (1908) teaches such an apparatus, but in Preston pressure roll means are employed in combination with his knives to compact material in the processed sheet which has been displaced by the action of the knives. The Preston knives are not driven and his apparatus is "especially designed for cutting material for making patterns which are . . . irregular in outline . . . F" (p.2, col. 1, lines 43-46 of Preston).
Underwood U.S. Pat. No. 647,053 (1900), Flory et al U.S. Pat. No. 3,138,049 (1964) and Hyatt et al U.S. Pat. No. 3,786,706 (1974) apparently teach cutting apparatus utilizing rotatable disc cutter pairs in combination with means causing individual cutters of a pair operate at differential rotational speeds. However, in such apparatus, the edges of each blade pair overlap, producing complete excision in cutting. Moreover, the sheet material being cut, such as wallpaper or the like, is evidently not self advanced by the cutting blade pair in a cutting operation.
Cutter apparatus which employs a pair of axially spaced, coplanar blades which are each driven in an opposite direction relative to the other under conditions such that a differential in peripheral blade edge speeds is maintained has not previously been known or suggested in this art, so far as is now known.